共查询到20条相似文献,搜索用时 0 毫秒
1.
Nonlinear Dynamics - A recursive identification method for discrete-time nonlinear cascade systems with a linear dynamic system followed by a time-varying output hysteresis is presented. The... 相似文献
2.
Nonlinear Dynamics - Unknown hysteresis cannot be ignored in containment control, but the problem of prescribed-time containment for uncertain nonlinear multi-agent systems with unknown hysteresis... 相似文献
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Nonlinear Dynamics - This paper addresses the consensus tracking problem of a class of nonlinear multi-agent systems by using observer-based control. The systems are in output-feedback form with... 相似文献
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Nonlinear Dynamics - The fractional-order derivative is a powerful and promising concept to describe many physical phenomena due to its heredity/memory feature. This paper aims to establish a... 相似文献
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This paper focuses on the identification problem of Wiener nonlinear systems with non-uniform sampling. The mathematical model for the Wiener nonlinear system is established from the non-uniformly sampled input–output data. In order to solve the identification problem of the Wiener nonlinear system with the unmeasurable variables in the information vector, the gradient-based iterative algorithm is presented by replacing the unmeasurable variables with their corresponding iterative estimates. Finally, the simulation results indicate that the proposed algorithm is effective. 相似文献
6.
Response analysis of randomly excited nonlinear systems with symmetric weighting Preisach hysteresis
应祖光 《Acta Mechanica Sinica》2003,19(4):365-370
An approximate method for analyzing the response of nonlinear systems with the Preisach hysteresis of the non-local memory
under a stationary Gaussian excitation is presented based on the covariance and switching probability analysis. The covariance
matrix equation of the Preisach hysteretic system response is derived. The cross correlation function of the Preisach hysteretic
force and response in the covariance equation is evaluated by the switching probability analysis and the Gaussian approximation
to the response process. Then an explicit expression of the correlation function is given for the case of symmetric Preisach
weighting functions. The numerical result obtained is in good agreement with that from the digital simulation.
The project supported by the National Natural Science Foundation of China (19972059) and Zhejiang Provincial Natural Science
Foundation (101046) 相似文献
7.
Nonlinear Dynamics - This work presents a new method for the identification of fractional-order nonlinear systems from time domain data. A parametric identification technique for integer-order... 相似文献
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Nonlinear Dynamics - The hysteretic behavior is an essential feature of many physical systems (e.g. mechanical structures, buildings dampers). Such a feature is conveniently accounted for in... 相似文献
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Nonlinear Dynamics - This article examines the fuzzy adaptive design and the sliding mode control issue for a class of quantized systems subject to input nonlinearities. We establish a new... 相似文献
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Nonlinear Dynamics - This paper proposes a non-intrusive interval uncertainty analysis method for estimation of the dynamic response bounds of nonlinear systems with uncertain-but-bounded... 相似文献
12.
Piecewise-linear restoring force surfaces for semi-nonparametric identification of nonlinear systems
A method for identifying a piecewise-linear approximation to the nonlinear forces acting on a system is presented and demonstrated using response data from a micro-cantilever beam. It is based on the Restoring Force Surface (RFS) method by Masri and Caughey, which is very attractive when initially testing a nonlinear system because it does not require the user to postulate a form for the nonlinearity a priori. The piecewise-linear fitting method presented here assures that a continuous piecewise-linear surface is identified, is effective even when the data does not cover the phase plane uniformly, and is more computationally efficient than classical polynomial based methods. A strategy for applying the method in polar form to sinusoidally excited response data is also presented. The method is demonstrated on simulated response data from a cantilever beam with a nonlinear electrostatic force, which highlights some of the differences between the local, piecewise-linear model presented here and polynomial-based models. The proposed methods are then applied to identify the force-state relationship for a micro-cantilever beam, whose response to single frequency excitation, measured with a Laser Doppler Vibrometer, contains a multitude of harmonics. The measurements suggest that an oscillatory nonlinear force acts on the cantilever when its tip velocity is near maximum during each cycle. 相似文献
13.
This paper discusses iterative identification problems for a class of output nonlinear systems (i.e., Wiener nonlinear systems) with moving average noises from input–output measurement data, based on the Newton iterative method. The basic idea is to decompose a nonlinear system into two subsystems, to replace the unknown variables in the information vectors with their corresponding estimates at the previous iteration, and to present a Newton iterative identification method using the hierarchical identification principle. The numerical simulation results indicate that the proposed algorithms are effective. 相似文献
14.
Methods that treat rigid/flexible multibody systems undergoing large motion as well as deformations are often accompanied with inefficiencies and instabilities in the numerical solution due to the large number of state variables, differences in the magnitudes of the rigid and flexible body coordinates, and the time dependencies of the mass and stiffness matrices. The kineto-static methodology of this paper treats a multibody mechanical system to consist of two collections of bulky (rigid) bodies and relatively flexible ones. A mixed boundary condition nonlinear finite element problem is then formulated at each time step whose known quantities are the displacements of the nodes at the boundary of rigid and flexible bodies and its unknowns are the deformed shape of the entire structure and the loads (forces and moments) at the boundary. Partitioning techniques are used to solve the systems of equations for the unknowns, and the numerical solution of the rigid multibody system governing equations of motion is carried out. The methodology is very much suitable in modelling and predicting the impact responses of multibody system since both nonlinear and large gross motion as well as deformations are encountered. Therefore, it has been adopted for the studies of the dynamic responses of ground vehicle or aircraft occupants in different crash scenarios. The kineto-static methodology is used to determine the large motion of the rigid segments of the occupant such as the limbs and the small deformations of the flexible bodies such as the spinal column. One of the most dangerous modes of injury is the amount of compressive load that the spine experiences. Based on the developed method, a mathematical model of the occupant with a nonlinear finite element model of the lumbar spine is developed for a Hybrid II (Part 572) anthropomorphic test dummy. The lumbar spine model is then incorporated into a gross motion occupant model. The analytical results are correlated with the experimental results from the impact sled test of the dummy/seat/restraint system. With this extended occupant model containing the lumbar spine, the gross motion of occupant segments, including displacements, velocities and accelerations as well as spinal axial loads, bending moments, shear forces, internal forces, nodal forces, and deformation time histories are evaluated. This detailed information helps in assessing the level of spinal injury, determining mechanisms of spinal injury, and designing better occupant safety devices. 相似文献
15.
Lionel Mathelin Luc Pastur Olivier Le Ma?tre 《Theoretical and Computational Fluid Dynamics》2012,26(1-4):319-337
We present a method that seeks to combine the properties of optimal control with the robust character of closed-loop control. The method relies on the availability of a reduced model of the system to be controlled, in order to express the control problem in a low-dimensional space where the system-state-dependent optimal control law is subsequently approximated in a preprocessing stage. A polynomial expansion is used for the approximation, enabling fast update of the optimal control law each time a new observation of the system state is made available. It results in a real-time compatible, efficient (optimal-like), and robust control strategy. A compressed-sensing approach is proposed to efficiently construct the approximate control law, exploiting the compressible character of the optimal control law in the retained approximation basis. The method is demonstrated for the control of the flow around a cylinder and is shown to perform as well as the much more costly receding-horizon optimal control approach, where the exact optimal control problem is actually recomputed, even in the presence of large aleatoric perturbations. Potential and remaining issues toward application to larger dimensional reduced systems are also discussed, and some directions for improvement are suggested. 相似文献
16.
In this paper, we first verify that fractional order systems using Caputo’s or Riemann–Liouville’s derivative can be represented by the continuous frequency distributed model with initial value carefully allocated. Then, the relation of the stability between the fractional order system and its corresponding integer order system is discussed and it is proven that stability of integer order system implies the stability of its corresponding fractional order system under some mild conditions. Moreover, we extend the stability theorems to the finite-dimensional case since fractional order systems are always implemented by approximation. Some illustrative examples are finally provided to show the usage and effectiveness of the proposed stability theorems. 相似文献
17.
It is observed that the harmonic balance (HB) method of parametric identification of nonlinear system may not give right identification
results for a single test data. A multiple-trial HB scheme is suggested to obtain improved results in the identification,
compared with a single sample test. Several independent tests are conducted by subjecting the system to a range of harmonic
excitations. The individual data sets are combined to obtain the matrix for inversion. This leads to the mean square error
minimization of the entire set of periodic orbits. It is shown that the combination of independent test data gives correct
results even in the case where the individual data sets give wrong results. 相似文献
18.
Nonlinear Dynamics - This work aims to provide a broad overview of computational techniques belonging to the area of artificial intelligence tailored for identification of nonlinear dynamical... 相似文献
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The chaos of nonholonomic systems with two external nonlinear nonholonomic constraints where the magnitude of velocity is
a constant and the magnitude of the velocity is a constant with a periodic disturbance, respectively, is completely identified
for the first time. The scope of the chaos study is extended to nonlinear nonholonomic systems. By applying the nonlinear
nonholonomic form of Lagrange’s equations, the dynamic equation is expressed. The existence of chaos in these two nonlinear
nonholonomic systems is first wholly proved by all numerical criteria of chaos, i.e., the most reliable Lyapunov exponents,
phase portraits, Poincaré maps, and bifurcation diagrams. Furthermore, it is found that the Feigenbaum number still holds
for nonlinear nonholonomic systems. 相似文献